| Byrnewallace UK Tax Advisors Limited | Professional & scientific | 2023 |
| C & D Properties Armagh Ltd | Construction | 2018 |
| C & F Contracts Ltd | Water & waste | 2006 |
| C & J Meats Limited | Manufacturing | 2001 |
| C & M Transport Ltd | Transport & logistics | 2022 |
| C Carr Transport Ltd | Transport & logistics | 2025 |
| C M Agri, Building Supplies and Hire Limited | Wholesale & retail | 2025 |
| C S Renewables Limited | Energy | 2018 |
| C&G Contracts Ltd | Construction | 2019 |
| C&S Heating Ltd | Manufacturing | 2025 |
| C.Hinks Transport Ltd | Transport & logistics | 2025 |
| C.P.O. Surveying Ltd | Professional & scientific | 2009 |
| Cabin Craft Ltd | Wholesale & retail | 2025 |
| Cabragh House Farms Ltd | Agriculture & fishing | 2011 |
| Cabragh Ltd | Agriculture & fishing | 2018 |
| Cabragh Poultry Limited | Agriculture & fishing | 2025 |
| Cadan Solutions Limited | Information & communication | 2005 |
| Cafe Olympus Ltd | Hospitality | 2018 |
| Cairns Consultants Ltd | Construction | 2023 |
| Caledon Social and Economic Development CIC | Other services | 2018 |
| Calkill International Ltd | Transport & logistics | 2018 |
| Call Tech Support Ltd | Information & communication | 2017 |
| Callan Cattle Ltd | Wholesale & retail | 2011 |
| Callan Holdings Limited | Real estate | 2017 |
| Callan Renewables Ltd | Energy | 2014 |
| Callan River Accommodation Ltd | Hospitality | 2022 |
| Callan Valley Trading Ltd | Wholesale & retail | 2025 |
| Cameron Durand Ltd | Financial services | 2025 |
| Campbell Bulk Haulage Limited | Transport & logistics | 2010 |
| Campbell Trade Sales Ltd | Wholesale & retail | 2017 |
| Capmam Limited | Other services | 2019 |
| Cardboard Box Co Ireland Ltd | Manufacturing | 2010 |
| Carna INV Ltd | Real estate | 2020 |
| Carnagh Livestock Ltd | Wholesale & retail | 2023 |
| Carrickabolie Farm Feeds Limited | Wholesale & retail | 2018 |
| Carrickbrackan Property Ltd | Real estate | 2025 |
| Carrickview Stud Limited | Agriculture & fishing | 2024 |
| Carrigmona Solar Limited | Energy | 2026 |
| Carrs Elite Foods Limited | Wholesale & retail | 2015 |
| Cartin's Coffee Limited | Hospitality | 2026 |
| Carty Assets Limited | Real estate | 2025 |
| Cashel Farm Ltd | Agriculture & fishing | 2023 |
| Cashel Hill Contracts Limited | Construction | 2024 |
| Cashel Truck Services Limited | Transport & logistics | 2012 |
| Caspac Distribution Ltd | Transport & logistics | 2018 |
| Cassey Logistics Ltd | Transport & logistics | 2025 |
| Castle Initiatives Limited | Construction | 2020 |
| Castle Stage Hire Ltd | Arts & recreation | 2012 |
| Castledillon Estate Ltd | Agriculture & fishing | 2020 |
| Castlehill Investors LLP | | 2014 |
| Castlerock Foods Ltd | Professional & scientific | 2000 |
| Castlewood Armagh Ltd | Real estate | 2012 |
| Catari Murphy Limited | Health & social care | 2025 |
| Cathal Smyth Ltd | Construction | 2025 |
| Cathy Services Ltd | Construction | 2023 |
| CAZ Direct Limited | Administrative & support | 2025 |
| CBT Sales & Services Limited | Wholesale & retail | 2012 |
| CC Automotive Parts Ltd | Wholesale & retail | 2018 |
| CC Safety Training (NI) Ltd | Administrative & support | 2025 |
| Ccee Limited | Construction | 2025 |
| CD Enterprises Ltd | Construction | 2023 |
| CD Frozen Bites Limited | Hospitality | 2020 |
| Cdgc Enterprises Ltd | Wholesale & retail | 2023 |
| Cdsr Limited | Wholesale & retail | 2023 |
| Celtic Ties Limited | Extraterritorial | 2005 |
| CFF Hardware Ltd | Construction | 2014 |
| CH Retail Ltd | Wholesale & retail | 2024 |
| Charlie's Chipper Ltd | Hospitality | 2023 |
| Checkweighscales.Com Ltd | Information & communication | 2018 |
| Chef KHY Ltd | Hospitality | 2020 |
| Cherrywood Joinery Ltd | Manufacturing | 2023 |
| China Junction Limited | Hospitality | 2024 |
| Chopsticks Richhill Ltd | Hospitality | 2022 |
| Chris Joinery Ltd | Construction | 2019 |
| Chronically Fabulous | Arts & recreation | 2017 |
| Cill Chluana Mechanical Ltd | Construction | 2025 |
| Circucel Liquid Dispensing System Limited | Manufacturing | 2026 |
| City Properties Newry Limited | Real estate | 2020 |
| City Rentals Ltd | Real estate | 2026 |
| CJH Salvage & Spares Limited | Water & waste | 2024 |
| CK Rafferty Solicitors Limited | Professional & scientific | 2013 |
| CK Sports Massage Ltd | Arts & recreation | 2024 |
| CKF Farms Limited | Agriculture & fishing | 2023 |
| Clady Aggregates Limited | Mining & quarrying | 2022 |
| Clady IT Solutions Ltd | Information & communication | 2021 |
| Clady Quarries Plant & Hire Ltd | Mining & quarrying | 2012 |
| Cladyglenn Properties Limited | Real estate | 2023 |
| Cladym Ltd | Hospitality | 2025 |
| Cladymilltown Supplies Ltd | Wholesale & retail | 2017 |
| Clarke Fitness Ltd | Arts & recreation | 2014 |
| Clay Fuels Limited | Wholesale & retail | 2012 |
| Clay View Canines Ltd | Agriculture & fishing | 2019 |
| Clea Construction Limited | Construction | 2022 |
| Clea Contracts Limited | Agriculture & fishing | 2024 |
| Clean Alternate Ltd | Professional & scientific | 2021 |
| Clean Luxury Ltd | Administrative & support | 2025 |
| Climbing Frame Factory Limited | Manufacturing | 2017 |
| Cloud Hosted Ltd | Information & communication | 2025 |
| CLS Signage, Interiors and Facility Management Limited | Wholesale & retail | 2015 |
| Cluain Holdings Ltd | Real estate | 2022 |